Jonckheere 900, a planetary nebula in Gemini

Jonckheere 900, a planetary nebula in Gemini

Image Credit: Josh Barrington, ESA/Hubble & NASA

Jonckheere 900 or J 900 (also known as PN G194.2+02.5) is a planetary nebula that lies about 16,000 light-years away from Earth in the constellation of Gemini (the Twins, Castor & Pollux), while it is receding from us at approximately 47 kilometers per second. It was discovered in the early 1900s by astronomer Robert Jonckheere.

When a star with a mass up to eight times that of the Sun runs out of fuel at the end of its life, it blows off its outer shells and begins to lose mass. This allows the hot, inner core of the star (collapsing from a red giant to a white dwarf) to radiate strongly, causing this outward-moving cocoon of gas to glow brightly. They are called “planetary” nebulae because early observers thought they looked like planets; the name got stuck even though they don’t have anything to do with planets at all.

Jonckheere 900 is a dusty, small but fairly bright nebula with a relatively evenly spread central region surrounded by soft wispy edges. Its central star is only just visible in this image, and is very faint (magnitude 17.8). The nebula appears to display a bipolar structure, where there are two distinct lobes of material emanating from its center, enclosed by a bright oval disk.

Jonckheere 900 has a nearby companion, a 13 magnitude star, which often causes problems for observers because it is so close to the nebula — when seeing conditions are bad, this star seems to merge into Jonckheere 900, giving it an elongated appearance, what can be confusing for observers. Sometimes the nebula and star are even mistaken for a double star in place of these two objects, as the planetary nebula is quite small and compact.

Planetary nebulae last for only about 10,000 years, a very short period in the 10-billion-year lifespan of Sun-like stars. So, over the next several thousand years, Jonckheere 900 will gradually disperse into space, and then the white dwarf will cool and fade away for billions of years. Our own Sun is expected to undergo a similar fate, but fortunately this will not occur until some 5 billion years from now.

This image is taken with the Wide Field Planetary Camera 2 onboard the Hubble Space Telescope using three different color filters. A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Josh Barrington.

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